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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

41679 results found.

  1. GRB 260619A: SVOM/VT optical counterpart confirmation
  2. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  3. GRB 260618B: SVOM/VT optical candidate
  4. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  5. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  6. Konus-Wind detection of GRB 260617A
  7. GRB 260616B: AstroSat CZTI detection
  8. GRB 260616A: AstroSat CZTI detection
  9. GRB 260616A: SVOM/GRM observation
  10. EP260618a: OHP/T193 optical observations
  11. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  12. GRB 260619A: Kilonova-Catcher optical upper limit
  13. EP260618a: EP-FXT follow-up observation
  14. EP260618a: LCO optical counterpart confirmation
  15. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  16. EP260618a: COLIBRÍ optical counterpart candidate
  17. GRB 260616A: NuSTAR detection of prompt emission
  18. GRB 260614B: NuSTAR detection of prompt emission
  19. GRB 260619A: SVOM possible detection of a faint burst
  20. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 260618B: Fermi-LAT detection
  22. IPN triangulation of GRB 260617A (short)
  23. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  24. GRB 260616A: Insight-HXMT detection
  25. EP260618a: EP-WXT detection of an X-ray transient
  26. GRB 260610B: AbAO optical observations
  27. EP260616a/GRB 260616B: EP-FXT follow-up observation
  28. GRB 260506B: cubesat Avion detection
  29. GRB 260616C: GECAM-B observation of a burst
  30. GRB 260617A: Fermi GBM Detection
  31. GRB 260616A: Fermi GBM Observation
  32. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  33. Konus-Wind detection of GRB 260616B/EP260616a
  34. Konus-Wind detection of GRB 260616A
  35. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  36. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  37. GRB 260616A: GECAM-B observation
  38. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  39. GRB 260429A: cubesat Avion detection
  40. GRB260616C: MAXI/GSC detection
  41. GRB 260616A: Fermi-LAT detection
  42. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  43. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  44. GRB 260614A: AstroSat CZTI detection
  45. EP260616a: EP-WXT detection of a fast X-ray transient
  46. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  47. The EP-WXT trigger 01709270148 is likely a flaring star
  48. GRB 260616B: Fermi GBM Detection
  49. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  50. The EP-WXT trigger 01709269893 is likely a flaring star
  51. GRB 260614B: SVOM/ECLAIRs refined analysis
  52. GRB 260610B: Terskol optical observations
  53. GRB 260614B: GECAM-B observation
  54. GRB 260610B: SVOM/GRM observation
  55. GRB 260614B: SVOM/VT optical afterglow confirmation
  56. GRB 260614B: Fermi GBM Observation
  57. GRB 260610B: ALMA detection
  58. GRB 260614A: GECAM-B observation
  59. GRB 260614B: SVOM/VT optical candidate from VHF data
  60. GRB 260614B: SVOM detection of a burst
  61. GRB 260611B: SVOM/GRM detection
  62. The EP-WXT trigger 01709269488 is likely a flaring star
  63. GRB 260603C: AstroSat CZTI detection
  64. GRB 260610B: further Liverpool Telescope optical observations
  65. GRB 260610B: Fermi GBM Observation
  66. GRB 260610B / AT2026owq: GRANDMA optical observations
  67. GRB 260610B / AT2026owq: further SAO RAS optical observations
  68. EP260605a: COLIBRÍ optical upper limits
  69. GRB 260610b: Liverpool Telescope optical observations
  70. EP260610b: Liverpool Telescope optical upper limits
  71. IceCube-260610A: No candidates from the Zwicky Transient Facility
  72. IceCube-260610A: EP-FXT follow-up observation
  73. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  74. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  75. GRB 260610B / AT2026owq: SVOM/VT optical observations
  76. GRB 260610B / AT2026owq: OASDG optical observations
  77. GRB 260610B: IAC-80 Optical observations
  78. GRB 260610B / AT2026owq: SAO RAS optical observations
  79. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  80. EP260610b: GTC likely spectroscopic redshift z = 1.10
  81. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  82. The EP-WXT trigger 01709269176 is likely a flaring star
  83. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  84. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  85. GRB 260610B / AT2026owq: Early ATLAS observations
  86. GRB 260610B: TRT optical observation
  87. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  88. EP260610b: COLIBRÍ optical observations
  89. GRB 260610B: DDOTI optical observations
  90. EP260610b: MAO/AZT-22 optical observations
  91. GRB 260610B: GOTO optical counterpart candidate
  92. EP260610b: NOT optical observation
  93. EP260610b: SVOM/VT optical confirmation with blue color
  94. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 260515A: SOAR optical observations
  96. EP260610b: Gemini North optical counterpart candidate
  97. EP260610a: SVOM/VT optical upper limits
  98. EP260610b: Einstein Probe detection of an X-ray transient
  99. Konus-Wind detection of GRB 260601A
  100. IPN triangulation of GRB 260601A (short/hard)

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